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1 Introduction

Massive distribution of real-time video content is one of the big challenges in theInternet. Nowadays, there are several proposals that approximate to this goal,but none of them provide a QoS (Quality of Service) comparable to the DVB(Digital Video Broadcasting). This is a direct consequence of the design of theInternet and an uneﬃcient use of the capacity of the network. The Internet wascreated to provide the so called best-eﬀort service that basically means that youcan transmit data through the network but the transmission time is unknowna priori. That time depends on several factors such as network failures, thenetwork load and, obviously, the amount of sent data. These two last factors aredirectly related to the capacity of the network, a term also refered as (network)bandwidth.

In order to provide an acceptable QoS in real-time streaming scenarios one of themost important requirements to fulﬁll is to have a lower bound of the network capacity.However, most of the current solutions fail to take advantage of this resource. One of thereasons is that IP multicast has not achieved the expected popularity. This forces contentsources to replicate the same data for diﬀerent receivers, resulting in a lineargrowth of the transmmited data when the number of receivers increases. Inthis situation, P2P (Peer-to-Peer) overlays can improve the performance of thereal-time streaming services: given that all peers manage (and thus can share) thesame content, the trasmission requirements at the source are drammaticallyreduced.

This work introduces P2PSP (Peer-to-Peer Straightforward Protocol). P2PSP is a setof transmission and machine behavior rules that helps increasing the QoS of real-timestreaming systems. Basically, the P2PSP mimics the IP multicast solution by takingadvantage of the transmission capacity of the peers which is typically wasted in pure C/S(Client/Server) services. We would like to stress that, although the P2PSP can be anstandalone solution for small scenarios, its performance can be increased in massivescenarios by taking advantage of both paradigms: the C/S model and the P2Pmodel.